JPS6339490A - Control apparatus for dc brushless motor - Google Patents

Abstract

PURPOSE:To enable operating DC brushless motor stably and with high efficiency and high power factor over a wide range of drive frequency by making a time constant of a low-pass filter variable and by changing said time constant with a DC brushless motor drive frequency. CONSTITUTION:A terminal voltage of a DC brushless motor 1 is shaped into almost sinusoidal waveforms by a low-pass filter 20 and said waveforms are compared with each other by respective comparators 3a-3c to obtain a positional signal. A rotor position decision means 4 judges positions of a rotor and a filter constant change means 21 detects a drive frequency by counting how many times the rotor comes to the same position for a certain period of time, and changes a time constant of the low-pass filter 20 according to said drive frequency. A conduction mode control means 5 decides a mode of conducting an armature winding of the DC brushless motor 1 on the basis of output of the rotor position decision means 4.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention relates to a control device for a DC brushless motor that detects the rotor position from the voltage induced in the armature winding and drives the motor body. It is.

[Conventional technology]

As an example of a conventional control circuit of this type, FIG. 6 shows a block diagram of a control device for a DC brushless motor disclosed in Japanese Patent Application Laid-Open No. 52-80415.

(Configuration) In the figure, 1 is a DC brushless motor body with a synchronous motor structure (hereinafter abbreviated as DCBLM), 2a, 2b, 2
c is each low-pass filter, 3a.

3b and 3c are respective comparators, 4 is a rotor position determining means, and 5 is a DCB from the output of the rotor position determining means 4.
This is a control means for determining the malt to be energized to the armature winding of the LMI. 6 is an energization switching means for applying a voltage to a predetermined armature winding according to the energization mode determined by the control means 5, and is composed of a drive circuit 7 and a switching element 8 for driving a switching element such as a power transistor. . FIG. 7 shows the configuration of one of the low-pass filters 2a, 2b, and 2c shown in FIG. 6. 9.10 is each resistor, and 11 is each capacitor.

(Operation) Next, the operation will be explained. Figure 8 (a), (b)
.

(C) shows a timing chart of each signal waveform of the control device -4-, and (a) is a phase voltage waveform diagram of the three-phase winding of DCBLMI. Since the voltage applied by the energization switching means 6 (FIG. 6) is pulse width modulated, it contains many harmonics. This waveform (Figure 81 is the waste filter 2a, 2
After passing through b and 2c, harmonics are removed and a substantially sinusoidal fundamental wave diagram (b) is obtained. This filter output and
Virtual neutral pyroelectricity (ff (ground level in waveform (b) diagram),
Figure (C) shows the output waveforms compared by each comparator 3a, 3b, and 3c. This waveform (C) diagram is used as a position signal to be manually inputted to the rotor position determination means 4, and based on the determined position, the control means 5 determines the energizing mode to which the voltage should be applied to the electric machine r winding of the DCBLMI. The timing for switching the energization mode is when an edge at which the comparator output is inverted is detected. Accordingly, the energization switching means 6 applies a voltage to a predetermined armature winding, thereby rotating the DCBLMI.

By the way, in the waveform (a) diagram, the ideal timing at which the energization mode is switched is at the position θ. 1- That is, the phase delay of the filters 2a, 2b, and 2c is 90 degrees, and the energization mode is switched immediately at the zero-cross point of the filter output. However, in the waveform (b) diagram, the amount of phase delay differs depending on the frequency, as can be seen from the characteristic example of frequency f versus phase angle φ of each of the low-pass filters 2a, 2b, and 2c shown in FIG. Furthermore, there is a delay from the actual cello cross point in the waveform (b) diagram until the outputs of the comparators 3a, 3b, and 3c are inverted, a time delay until the position determination means 4 determines the position, and a time delay until the control means 5 receives the energization mode switching signal. Since there is a delay d, which is the sum of the delay until output and the delay from when the energization switching means 6 receives the energization mode switching signal to when the switching element 8 is switched, the energization mode is switched as shown in FIG. This is the point indicated by the dashed line. The phase delay amount of each filter 2a, 2b, 2c is -9
Since it is smaller than 0°, the sum of the delay of the filter and the delay with the control system may match the ideal timing of -90° delay, but only at one point at a certain frequency,
If the frequency variable range is widened, there will be a frequency range where the deviation from ideal timing will be large and the operation will become unstable.

[Problem that the invention seeks to solve]

Since the conventional DCBLM control device was configured as described above, the position detection accuracy and, by extension, the DCBLM energization mode switching timing are greatly influenced by the phase characteristics of each low-pass filter, and the frequency = J variation range is greatly influenced by the phase characteristics of each low-pass filter. There have been problems such as not being able to drive the motor widely, or not being able to drive the DCBLM stably, and furthermore, the efficiency and power factor of the motor are reduced.

This invention was made to solve the above-mentioned problems, and aims to provide a DCBLM 1111 control circuit that has a wide frequency variation range, stable operation, and good efficiency and power factor. The purpose is

[Means for solving problems]

Therefore, in the DCBLM control device according to the present invention, the time constant of the low-pass filter is made variable, and this time constant is switched according to the driving frequency of the DCBLM, thereby achieving the above object. It is something to do.

[Effect]

With the above configuration, the DCBLM in this invention
The control device switches the time constant of the low-pass filter according to the driving frequency of the DCBLM, changes the phase delay caused by the low-pass filter, and suppresses the deviation from the ideal timing of the switching timing of the energization mode as much as possible. Stable and highly efficient D CB LM over a range of driving frequencies.
It becomes possible to operate at a high power factor.

[Embodiments of the invention]

Hereinafter, the present invention will be explained based on examples. FIG. 1 shows a block diagram of an embodiment of a DCBLM control device according to the present invention. Same as the previous conventional example Fig. 6
(Equivalent) constituent elements are indicated by the same reference numerals.

(Configuration) In the figure, 1 is a DCBLM, 20 is a low-pass filter, 3a, 3b, 3c are comparators, 4 is a rotor position determination means, 5 is a control means that determines the energization mode based on the position determination result, Reference numeral 21 denotes a filter constant changing means that counts the driving frequency from the position determination result and outputs a filter constant changing signal based on the result. 4,5.21 is
This is realized by the microcomputer 22.

Reference numeral 6 denotes an energization switching means that applies a voltage to the predetermined 4 windings of the electric machine according to the energization mode determined by the control means 5, and includes a drive circuit 7 that drives a switching element 8 such as a power transistor, and a switching element f8. Consists of. FIG. 2 shows a specific configuration example of the low-pass filter 20. 23a.

23b, 23c; 24a, 24b, 24c are each resistance,
25a, 25b, 25c; 26a.

26b and 26c are respective capacitors, and 27a.

27b and 27c are respective relays.

(Operation) Next, the operation will be explained. The terminal voltage of DCBLMI has a substantially sinusoidal waveform due to the low-pass filter 20,
This waveform is sent to each comparator 3a.

By comparing 3b and 3c, a position signal can be obtained. This waveform is shown in Fig. 8 (a), (b), (C).
From the above position signal which is similar to
determines the position of the rotary reconnaissance, and the filter constant changing means 21 determines the drive frequency by counting how many times the rotor is at the same position in a certain period of time, and turns on each relay 27a, 27b, 27c below a certain frequency fc. and turn it off above fc to change the time constant. This operation sequence flowchart is shown in FIG.

Frequency f of low-pass filter 20 when changing the time constant
A characteristic diagram of the phase angle φ is shown in FIG.

The dotted line 30a indicates the case when the relays 27a, 27b, and 27c are turned on, and 30b indicates the case when they are turned off, and the frequency f
c and each relay 27a, 27b.

The characteristics when 27c is turned on/off are as shown by a solid line 31.

On the other hand, each comparator 3a, 3b.

3c, the timing at which the energization mode is switched, including the delay in the position determination means 4, the control means 5 that determines the energization mode, and the energization switching means 6, is as shown by the dashed line 32 in the figure, and the timing at which the energization mode is switched is as shown by the dashed line 32 in the same figure, and the timing is as follows: This can prevent the switching timing from deviating further from the ideal switching timing of -90°.

FIG. 5 is a block diagram of a low-pass filter 20 according to another embodiment of the present invention. 23a, 23b.

23c; 24a, 24b, 24c are each resistor, 25a, 2
5b, 25c; 26a, 26b.

26c is each capacitor, and 35a, 35b, and 35c are each semiconductor analog switch.

Regarding operation, relays 27a and 27b.

Since this is the same as the case of the first embodiment using 27c, repeated explanation will be omitted.

〔Effect of the invention〕

As described above, according to the present invention, the time constant of the low-pass filter is made variable and switched depending on the DC brushless motor drive frequency, thereby stabilizing the motor.
We were able to provide a control device that can be driven with high efficiency and high power factor.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a DC brushless motor control device according to an embodiment of the present invention, FIG. 2 is a configuration diagram of a low-pass filter, and FIG. 3 is an operation sequence flowchart.
FIG. 4 is a diagram showing the characteristics of the low-pass filter of the above embodiment, FIG. 5 is a configuration diagram of a low-pass filter according to another embodiment of the present invention, and FIG. 6 is a diagram showing the characteristics of the low-pass filter of the conventional DC brushless motor. 7 is a configuration diagram of a conventional low-pass filter, FIG. 8 is an operation waveform timing chart of a conventional DC brushless motor control device, and FIG. 9 is a diagram of a conventional low-pass filter.
FIG. 2 is a characteristic diagram of a conventional low-pass filter. 1...DC brushless motor (DCBLM) 3
a, 3b, 3c...Cobalator 4...
Rotation r゛ position determining means 8... Switching element Fig. 1 20... Low pass filter 21... Filter constant changing means 25 a,
25 b, 26 c------Capacitor 27
a, 27 b, 27 c...Relay (
switching element)

Claims (5)

[Claims] (1) A low-pass filter with a variable time constant that removes harmonic components from the three-phase armature winding terminal voltage, a comparator that compares the filter output with a virtual neutral point potential, and rotation from the comparator output. means for determining the rotor position; a frequency counting means for counting the frequency of the voltage applied to the winding from the output of the rotor position determining means; 1. A control circuit for a DC brushless motor, comprising filter constant control means for changing a time constant of a pass filter. (2) The low-pass filter has resistors connected in series connected in a three-phase star shape, a first capacitor connected in parallel with the resistor connected to the neutral point of the star shape, and further, The DC brushless motor according to claim 1, characterized in that a second capacitor connected in series and a switching element capable of transmitting an analog signal are connected in parallel with the first capacitor. control device. (3) Claim 1, wherein the switching element capable of transmitting the analog signal is a relay.
A control device for a DC brushless motor according to items 1 and 2. (4) The DC brushless motor control device according to claims 1 and 2, wherein the switching element capable of transmitting the analog signal is a semiconductor analog switch. (5) Claims 1 to 3, or claim 1, wherein the rotor position determining means, frequency counting means, and filter constant control means are realized by a microcomputer. DC described in paragraphs 2 and 4
Brushless motor control device.